Numerous regional and sub-regional divisions have since been defined to distinguish various cultures through time and space, as later archaeologists recognized that these generalised stages did not adequately correspond to the cultural variation that existed in different locations in the Americas.[1]

Defined by the ostensible prevalence of big-game hunting. In most places, this can be dated to before 8000 BCE, starting most probably around 16,500 BCE (see Paleo-Indians). Examples include the Clovis culture and Folsom tradition groups.

Defined as "early civilizations", and typically dating from 500 to 1200 CE. Willey and Phillips considered only cultures from Mesoamerica and Peru to have achieved this level of complexity. Examples include the early Maya and the Toltec.

Defined as "later prehispanic civilizations" and typically dated from 1200 CE until the advent of European colonisation. The late Maya and the Aztec cultures were Post-Classic.

Today, for Meso- and Andean South America, the later periods are more often classified using the "Horizon" terminology, with "Early Horizon" typically broadly equating to the Late Formative stage. "Horizons" are periods of cultural stability and political unity, with "Intermediate periods" covering the politically fragmented transition between them. In the Andes, there are three Horizon periods, with two Intermediate periods between them. The Horizons, and their dominant cultures are: Early Horizon, Chavin; Middle Horizon, Tiwanaku and Wari culture; Late Horizon, Inca.[2]

Since 1990, in the United States, physical anthropology and archaeological investigations based on the study of human remains are complicated by the Native American Graves Protection and Repatriation Act, (NAGPRA), which provides for the bodies of Native Americans and associated grave goods to be turned over to the recognized tribal body most legally affiliated with the remains. In some cases, notably, that of Kennewick Man, these laws have been subject to close judicial scrutiny and great intellectual conflict.[3]

Molecular genetics study suggests that survivingAmerindian populations derived from a theoretical single founding population, possibly from only 50 to 70 genetic contributors[7] Preliminary research, restricted to only 9 genomic regions (or loci) have shown a genetic link between original Americas and Asia populations. The study does not address the question of separate migrations for these groups, and excludes other DNA data-sets.[8]

The American Journal of Human Genetics released an article in 2007 stating "Here we show, by using 86 complete mitochondrialgenomes, that all Indigenous American haplogroups, including Haplogroup X (mtDNA), were part of a single founding population."[9] Amerindian groups in the Bering Strait region exhibit perhaps the strongest DNA or mitochondrial DNA relations to Siberian peoples. The genetic diversity of Amerindian indigenous groups increase with distance from the assumed entry point into the Americas.[10][11] Certain genetic diversity patterns from West to East suggest at least some coastal migration events.[12] Geneticists have variously estimated that peoples of Asia and the Americas were part of the same population from 42,000 to 21,000 years ago.[13]